308-07A-1

Four Wheel Drive (4WD) Systems

308-07A-1

DIAGNOSIS AND TESTING
Four Wheel Drive (4WD) Systems —Electronic Shift
Refer to Wiring Diagrams Cell 34, Electric Shift
Control for schematic and connector information.
Refer to Wiring Diagrams Cell 59, GenericElectronic Module (GEM) for schematic andconnector information.
Special Tool(s)Fluke 77-IV Digital Multimeter
FLU77-4 or equivalent

Vacuum Pump
014-R1054 or equivalentWorldwide Diagnostic System(WDS)
418-F224,
New Generation STAR (NGS)
Tester418-F052, or equivalentdiagnostic tool

Principles of Operation
Transfer Case — Electronic Shift
The four-wheel drive, electronic shift-on-the-fly
feature electrically shifts the vehicle transfer casebetween 2WD, 4X4, and 4X4 LOW. The systemmode is selected by the operator through the mode
select switch (MSS) on the instrument panel. The
operator is informed which mode the system is in
by two instrument cluster indicators, one for 4X4,
and one for 4X4 LOW in 4X4 LOW both the lamps
are on). Shifts into 4X4 can be made at any speed.
When shifting into 4X4 with the vehicle stationary,
tooth blockage may occur, preventing shiftcompletion. When the vehicle is driven above 8km/h (5mph) the shift will complete. When shiftingin or out of 4X4 LOW, the four-wheel drive (4WD)
control module requires that the vehicle speed beless than 5 km/h (3 mph), the brake pedal beapplied, and the transmission in NEUTRAL(automatic transmission) or the clutch pedal be
depressed (manual transmission). (The digitaltransmission range TR sensor informs the 4WD
control module when the automatic transmission isin the NEUTRAL range position.)
The gearmotor encoder assembly is mounted
externally on the transfer case. It drives a rotary
cam which moves the mode fork and the range fork
within the transfer case between the 4X4, 4X4
LOW, and 2WD range positions.
The 4WD control module uses two relays to control
the gearmotor encoder assembly shift between 4X4,
4X4 LOW, and 2WD modes. The 4WD control
module controls the pulse vacuum hublock (PVH)
solenoid which supplies engagement anddisengagement vacuum to control the hublocks.
The 4WD control module accomplishes shifts byinterpreting inputs from:• MSS• vehicle speed signal (transmitted from the ABS
system)• gearmotor encoder plate position• brake pedal switch• digital TR sensor (automatic transmission)• clutch pedal position (CPP) switch (manualtransmission)• ignition switch

Copyright  2002, Ford Motor Company
Last updated: 11/6/2008

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Four Wheel Drive (4WD) Systems

308-07A-2

DIAGNOSIS AND TESTING (Continued)
Based on these inputs, the 4WD control module
controls the shifts into 2WD, 4X4, or 4X4 LOW
with the following outputs:• low to high relay (clockwise)• high to low relay (counterclockwise)• pulse vacuum hublock (PVH) solenoid• gearmotor encoder assembly

The electronic shift-on-the-fly (ESOF) system has afeature which allows the driver to override thevacuum-operated hublocks. When the front hublocks
are manually turned to the LOCK position, thehublocks are locked at all times, overriding thevacuum operated system. If the front hublocks aremanually turned to the AUTO position, the hublocks
can only be locked by turning the MSS to 4X4 or
4X4 LOW position.

Electronic Shift Vacuum Schematic

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Four Wheel Drive (4WD) Systems

308-07A-3

DIAGNOSIS AND TESTING (Continued)
Hublock Operation
The 4X4 ESOF system uses timed vacuum
sequences to lock and unlock the wheel ends. A
high vacuum level is used to engage the hublocks,
and a lower vacuum level is used to disengage thehublocks, after which the vacuum is released andthe hublock holds itself in the proper mode. The
vacuum signals are supplied to the hublocks bysystem components, including the 4WD control
module, wiring harness, solenoid, vacuum harness
and vacuum seals. As the first step in service,eliminate such obvious items as loose wiring
connectings, loose vacuum connections, or damaged
vacuum lines.
Disengage Time‘‘Slow’’ release of the hublocks is not consideredabnormal for this system. Anytime vacuum isapplied to the hubs, whether for 4X4 or 4X2, thehublocks will initially engage. If 4X4 wasrequested, the hublocks will remain engaged, but if
4X2 was selected, the internal mechanism will
release only after the 4WD control module timers
expire and vacuum is vented from the hub. This
normally takes 15 seconds, but can take up to two
minutes, depending on how the 4X4 mode selectswitch was operated. After the hub mechanism
releases, internal springs must work the hublock
gears to the disengaged position. Road bumps,
vehicle speed, acceleration cycles, or momentary
reversal of direction can assist this process, varying
the length of time the hublocks remain engaged ineach situation.

Many system components are involved in the proper
operation of the ESOF hubs. Before diagnosing the
hublocks themselves as the cause of 4X4 concerns,
be sure to verify all related system components.
After removing the hublock retaining ring be sure
not to use tools other than hands or ‘‘grip’’ gloves
to remove the hublock, as damage may occur toeither the paint or the function of the hublock.
Pliers or locking Channel-Locks should beconsidered as a last resort, and will usually damage
the hublock, making it necessary to install a new
hublock.
Inspection and Verification — Electronic
Shift
1.

Visual Inspection Chart
MechanicalElectrical• Hublocks— installed— correct type
• Axle shafts anduniversal joints• Driveshaft and universal
joints• Shift linkage• Fluid leaks• Matching tire size
• Vacuum harness• Central junction box(CJB) fuse(s):— 19 (10A) (lateproduction)/(5A)(6.0L Diesel)— 27 (15A)— 31 (15A)— 33 (15A)— 34 (10A) (early
production)— 111 (30A)• 4WD control module• Pulse vacuum hublock(PVH) solenoid• Wiring harness• Mode select switch(MSS)• Gearmotor encoder
assembly• Connector(s)• Shift relays• Circuitry

Manual Override
The hublocks have manual override selector dials,
which, when rotated to the ‘‘LOCK’’ position, willkeep the mechanism locked regardless of the
instrument panel 4X4 mode select switch position.
Verify that both dials are in ‘‘AUTO’’ before
evaluating ESOF operation.
Hublock Replacement
Left and right side hublocks are not connected,
other than by the common vacuum supply line. If amalfunction in either hublock is diagnosed, it should
be installed as an individual unit; there is no needto ‘‘balance’’ an axle with new hublocks on bothsides. If both sides appear to be malfunctioning, besure to verify upstream integrity before installing
new hublocks on both sides.

Visually inspect for the following obvious signsof mechanical and electrical damage.

2.

If the concern remains after the inspection,connect the diagnostic tool to the data linkconnector (DLC) located beneath the instrument
panel and select the vehicle to be tested fromthe diagnostic tool menu. If the diagnostic tool
does not communicate with the vehicle:• check that the program card is correctly
installed.
• check the connections to the vehicle.
• check the ignition switch position.
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308-07A-4

Four Wheel Drive (4WD) Systems

308-07A-4

DIAGNOSIS AND TESTING (Continued)
3.

If the diagnostic tool still does not communicate
with the vehicle, refer to the diagnostic tool
manual.

4.

Carry out the DATA LINK DIAGNOSTICS
test. If the diagnostic tool responds with:• CKT914, CKT915 or CKT70 = ALL ECUSNO RESP/NOT EQUIP, refer to Section
418-00.
• NO RESP/NOT EQUIP for 4WD control
module, GO to Pinpoint Test D.

5.

If the DTCs retrieved are related to the concern,
go to the 4WD control module Diagnostic
Trouble Code (DTC) Index to continue
diagnostics.

6.

If no DTCs related to the concern are retrieved,carry out the electronic shift function test. Refer
to Function Test — Electronic Shift in thissection.

GEM Diagnostic Trouble Code (DTC) Index• NOTE: To carry out the 4WD control
module self-test for Excursion requires theheadlamps to be in the OFF position. Allothers require the headlamps to be in the ON
position.
SYSTEM PASSED, retrieve and record thecontinuous diagnostic trouble codes (DTCs),
erase the continuous DTCs and carry out the
4WD control module self-test.
GEM Diagnostic Trouble Code (DTC) Index
DTC

Description

SourceAction

B1317

Battery Voltage High4WD Control Module

REFER to Section 414-00.

B1318

Battery Voltage Low

4WD Control Module

REFER to Section 414-00.

B1342

ECU is Defective

4WD Control Module

CLEAR DTCs. REPEAT
the self-test. If DTC B1342
is retrieved, INSTALL a
new 4WD control module.
REFER to Four Wheel
Drive (4WD) Control
Module in this section.
CLEAR the DTCs.
REPEAT the self-test.

B1355

Ignition RUN Circuit
Failure4WD Control Module

REFER to Section 211-05.

B1359

Ignition RUN/ACC Circuit
Failure4WD Control Module

REFER to Section 211-05.

B1366

Ignition START Circuit
Short to Ground

4WD Control Module

REFER to Section 211-05.

B1483

Brake Pedal Input Circuit
Failure4WD Control Module

REFER to Section 417-01.

B1485

Brake Pedal Input Circuit
Short to Battery

4WD Control Module

REFER to Section 417-01.

B2477

Module Configuration
Failure (Unconfigured,
Incorrect or Rejected)

4WD Control Module

REFER to Section 418-01.

C1728

Transfer Case Unable toTransition Between 2H and
4H

4WD Control Module

GO to Pinpoint Test C.

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308-07A-5

Four Wheel Drive (4WD) Systems

308-07A-5

DIAGNOSIS AND TESTING (Continued)
GEM Diagnostic Trouble Code (DTC) Index (Continued)
DTC

Description

SourceActionC1729

Transfer Case Unable toTransition Between 4H and
4L

4WD Control Module

GO to Pinpoint Test C.

P0500

Vehicle Speed Sensor(VSS) Malfunction

4WD Control Module

REFER to Section 206-09.

P1804

Transmission 4-Wheel
Drive High Indicator
Circuit Failure

4WD Control Module

GO to Pinpoint Test H.

P1806

Transmission 4-Wheel
Drive High Indicator Short

4WD Control Module

GO to Pinpoint Test H.

P1808

Transmission 4-Wheel
Drive Low Indicator
Circuit Failure

4WD Control Module

GO to Pinpoint Test I.

P1810

Transmission 4-Wheel
Drive Low Indicator Short

4WD Control Module

GO to Pinpoint Test I.

P1812

Transmission 4-Wheel
Drive Mode Select Circuit
Failure4WD Control Module

GO to Pinpoint Test E.

P1815

Transmission 4-Wheel
Drive Mode Select Short

4WD Control Module

GO to Pinpoint Test E.

P1819

Transmission Neutral
Safety Switch Short Circuit
to Ground

4WD Control Module

GO to Pinpoint Test F.

P1820

Transmission Transfer Case
Clockwise Shift Relay

4WD Control Module

GO to Pinpoint Test E.

P1822

Transmission Transfer Case
Clockwise Shift Relay Coil

4WD Control Module

GO to Pinpoint Test E.

P1828

Transmission Transfer Case
Counterclockwise Shift

4WD Control Module

GO to Pinpoint Test E.

P1830

Transmission Transfer Case
Counterclockwise Shift

4WD Control Module

GO to Pinpoint Test E.

P1832

Transmission Transfer Case
Differential Lock-Up

4WD Control Module

GO to Pinpoint Test G.

P1834

Transmission Transfer Case
Differential Lock-Up

4WD Control Module

GO to Pinpoint Test G.

P1865

Transmission Transfer Case
Contact Plate Power

4WD Control Module

GO to Pinpoint Test E.

P1866

Transmission Transfer Case
System Concern

4WD Control Module

GO to Pinpoint Test C.

P1867

Transmission Transfer Case
Contact Plate General

4WD Control Module

GO to Pinpoint Test E.

P1876

Transmission Transfer Case
2-Wheel Drive Solenoid
Circuit Failure

4WD Control Module

GO to Pinpoint Test G.

P1877

Transmission Transfer Case
2-Wheel Drive Solenoid
Circuit Short

4WD Control Module

GO to Pinpoint Test G.

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308-07A-6

Four Wheel Drive (4WD) Systems

308-07A-6

DIAGNOSIS AND TESTING (Continued)
Functional Test — Electronic ShiftPINPOINT TEST C: ELECTRONIC SHIFT FUNCTIONAL TESTNOTICE: The function test must be carried out on a hard surface in a vacant area
without traffic.
C1

C2

Test StepCHECK FOR 2WD INDICATED• Make sure the hublocks are in the AUTO position.
• Start the vehicle and allow to idle.
• Apply the brake pedal and hold.
• For automatic transmission, shift the transmission to NEUTRAL.
For manual transmission, press and hold the clutch pedal.
• Turn the mode select switch (MSS) to 2WD while holding theshift conditions.
• Observe the 4X4 and 4X4 LOW indicators.
• Are both indicators off?
CHECK FOR THE PRESENCE OF 4X4
NOTICE: Make sure there is a clear area behind the vehicle
before backing up.
Shift the transmission to REVERSE and back the vehicle up 3.0
meters (10 feet) to relieve driveline wind-up.
• Drive the vehicle forward for 3.0 meters (10 feet) and stop.
• Press the brake pedal and hold.
• For automatic transmission, shift the transmission to NEUTRAL.
For manual transmission, press and hold the clutch pedal. Holdthe shift conditions for 20 seconds.
• Execute tight turns on a hard surface.
• Check for the presence of driveline wind-up and tire scuff.
• Is driveline wind-up and tire scuff present?
CHECK INDICATOR PROVE-OUT• Ignition OFF.
• Turn the ignition switch to start and observe the 4X4 and 4X4
LOW indicators for prove-out.
• Did the indicators prove out?
•

C3

C4

C5

C6

VERIFY SHIFT TO 4X4• Turn the MSS to 4X4.
• Listen for relay clicks and gearmotor operation.
• Wait for 20 seconds after the MSS is turned to 4X4. (Thesystem will use up to five cycles of shift attempts trying toengage 4X4.)• Is the 4X4 indicator ON?
ATTEMPT MECHANICAL ASSIST ENGAGEMENT• Drive the vehicle above 8 kmh (5 mph) for at least 20 seconds.
• Stop the vehicle.
• Observe the 4X4 indicator.
• Is the 4X4 indicator ON?

CHECK FOR MECHANICAL ENGAGEMENT OF 4X4• Drive the vehicle for two minutes above 16 kmh (10 mph).
• Execute tight turns on a hard surface.
• Check for the presence of driveline wind-up and tire scuff.
• Is driveline wind-up and tire scuff present?

Result / Action to TakeYes

GO to C3.

No

GO to C2.

Yes

RETRIEVE 4WD Control Module self-test
DTCs. If a self-test DTC related to theconcern is retrieved, REFER to 4WD
Control Module Diagnostic Trouble Code
(DTC) Index. If no DTC is retrieved,
REFER to Section 308-07B and REPAIR
the transfer case as necessary.

No

If the 4X4 indicator is ON, GO to Pinpoint
Test E. If the 4X4 LOW indicator is ON,
GO to Pinpoint Test F.

Yes

GO to C4.

No

REPAIR the instrument cluster asnecessary. REFER to Section 413-01.

Yes

GO to C6.

No

GO to C5.

Yes

GO to C6.

No

RETRIEVE the 4WD control module
self-test DTCs. If a self-test DTC related tothe concern is retrieved, REFER to the
4WD Control Module Diagnostic Trouble
Code (DTC) Index. If no DTC related tothe concern is retrieved, GO to C9.

Yes

GO to C9.

No

4X4 did not mechanically engage.
RETRIEVE 4WD control module self-test
DTCs. If a self-test DTC related to theconcern is retrieved, REFER to the 4WD
Control Module Diagnostic Trouble Code
(DTC) Index. If no DTC related to theconcern is retrieved, GO to C7.

(Continued)
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308-07A-7

Four Wheel Drive (4WD) Systems

308-07A-7

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST C: ELECTRONIC SHIFT FUNCTIONAL TEST (Continued)
C7

C8

Test StepCHECK FOR FRONT AXLE ENGAGEMENT• Raise and support the front tires off the ground until they can be
spun freely. Refer to Section 100-02.
• Rotate the left front tire one revolution forward and one
revolution backward while observing the left front axle shaft anduniversal joint.
• Rotate the right front tire one revolution forward and one
revolution backward while observing the right front axle shaft
and universal joint.
• Did both front axle shafts rotate?
CHECK FOR FRONT AXLE/DIFFERENTIAL ENGAGEMENT• Rotate the front driveshaft.
• Does either front axle shaft turn?

Result / Action to TakeYes

GO to C8.

No

GO to Pinpoint Test G.

Yes

GO to Pinpoint Test E.

No

REPAIR the front differential or axle asnecessary. REFER to Section 205-03.
C9C10

CHECK FOR CORRECT INDICATOR OPERATION ON 4X4 LOW
ENGAGEMENT• While driving the vehicle forward above 8 kmh (5 mph), turn the
MSS to 4X4 LOW while observing the indicators for fiveseconds.
• Shift the MSS to 4X4.
• Stop the vehicle and apply the parking brake.
• For automatic transmission, shift the transmission to PARK andrelease the brake pedal. For manual transmission, shift thetransmission to NEUTRAL and release the clutch pedal.
• Did the 4X4 LOW indicator stay off?
CHECK THE 4X4 LOW INDICATOR ON IN ERROR• Turn the MSS to 4X4 LOW.
• Apply and hold the brake pedal.
• Is the 4X4 LOW indicator OFF?

Yes

GO to C10.

NoRETRIEVE 4WD control module self-test
DTCs. If a self-test DTC related to theconcern is retrieved, REFER to the 4WD
Control Module Diagnostic Trouble Code
(DTC) Index. If no DTC related to theconcern is retrieved, GO to Pinpoint Test
I.

Yes

GO to C11.

No

RETRIEVE 4WD control module self-test
DTCs. If a self-test DTC related to theconcern is retrieved, REFER to the 4WD
Control Module Diagnostic Trouble Code
(DTC) Index. If no DTC related to theconcern is retrieved, GO to Pinpoint Test
I.
C11

C12

CHECK THE 4X4 LOW INDICATOR FOR ON IN 4X4 LOW• For automatic transmission, shift the transmission to NEUTRAL.
For manual transmission, press and hold the clutch pedal.
• Listen for relay clicks and gearmotor operation.
• Hold the shift conditions for 20 seconds. (The system will use up
to five cycles of shift attempts trying to engage 4X4 LOW.)• Is the 4X4 LOW indicator ON?
ATTEMPT MECHANICAL ASSIST OF 4X4 LOW ENGAGEMENT
•

•
•
•
•
•

NOTICE: Make sure there is a clear area behind the vehicle
before backing up.
Shift the transmission to REVERSE and back the vehicle up 3.0
meters (10 feet) to relieve driveline wind-up and stop.
Drive the vehicle forward for 3.0 meters (10 feet) and stop.
Apply the brake pedal and hold.
For automatic transmission, shift the transmission to NEUTRAL.
For manual transmission, press the clutch pedal and hold. Holdall shift conditions for 20 seconds.
Observe the 4X4 LOW indicator.
Is the 4X4 LOW indicator ON?

Yes

GO to C13.

No

GO to C12.

Yes

GO to C13.

No

RETRIEVE 4WD control module self-test
DTCs. If a self-test DTC related to theconcern is retrieved, REFER to the 4WD
Control Module Diagnostic Trouble Code
(DTC) Index. If no DTC related to theconcern is retrieved, GO to Pinpoint Test
F.

(Continued)

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308-07A-8

Four Wheel Drive (4WD) Systems

308-07A-8

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST C: ELECTRONIC SHIFT FUNCTIONAL TEST (Continued)
C13

C14

C15

Test StepCHECK FOR MECHANICAL ENGAGEMENT OF 4X4 LOW• NOTE: Driveline wind-up and tire scuff is present in both 4X4
and 4X4 LOW. However, vehicle speed is severely limited in
4X4 LOW.
Execute tight turns on a hard surface.
• Check for the presence of driveline wind-up, tire scuff andreduced vehicle speed.
• Is driveline wind-up, tire scuff and reduced speed present?

CHECK FOR CORRECT INDICATOR OPERATION ON 4X4 LOW
DISENGAGEMENT• While driving the vehicle forward above 8 km/h (5 mph), turn the
MSS to 4X4 while observing the indicators.
• Turn the MSS to 4X4 LOW.
• Stop the vehicle and apply the parking brake.
• For automatic transmission, shift the transmission to PARK andrelease the brake pedal. For manual transmission, shift thetransmission to NEUTRAL and release the clutch pedal.
• Is the 4X4 LOW indicator ON?

CHECK THE 4X4 LOW INDICATOR• Turn the MSS to 4X4.
• Apply and hold the brake pedal.
• Is the 4X4 LOW indicator ON?

Result / Action to TakeYes

GO to C14.

No

4X4 LOW did not mechanically engage.
RETRIEVE 4WD control module self-test
DTCs. If a self-test DTC related to theconcern is retrieved, REFER to the 4WD
Control Module Diagnostic Trouble Code
(DTC) Index. If no DTC related to theconcern is retrieved, GO to Pinpoint TestF.

Yes

GO to C15.

No

RETRIEVE 4WD control module self-test
DTCs. If a self-test DTC related to theconcern is retrieved, REFER to the 4WD
Control Module Diagnostic Trouble Code
(DTC) Index. If no DTC related to theconcern is retrieved, GO to Pinpoint TestF.

Yes

GO to C16.

No

RETRIEVE 4WD control module self-test
DTCs. If a self-test DTC related to theconcern is retrieved, REFER to the 4WD
Control Module Diagnostic Trouble Code
(DTC) Index. If no DTC related to theconcern is retrieved, GO to Pinpoint Test
I.
C16

C17

C18

CHECK FOR 4X4 LOW INDICATOR OFF IN 4X4• Press and hold the brake pedal.
• For automatic transmission, shift the transmission to NEUTRAL.
For manual transmission, press and hold the clutch pedal.
• Listen for relay clicks and gearmotor operation.
• Hold the shift conditions for 20 seconds. (The system will use up
to five cycles of shift attempts trying to engage 4X4.)• Is the 4X4 LOW indicator OFF?
ATTEMPT MECHANICAL ASSIST OF 4X4 LOW
DISENGAGEMENT• Drive the vehicle forward above 8 kmh (5 mph) for at least fiveseconds.
• Stop the vehicle.
• Apply the brake pedal and hold.
• For automatic transmission, shift the transmission to NEUTRAL.
For manual transmission, press the clutch pedal and hold. Holdall shift conditions for 20 seconds.
• Observe the 4X4 LOW indicator.
• Is the 4X4 LOW indicator OFF?

Yes

GO to C18.

No

GO to C17.

Yes

GO to C18.

No

RETRIEVE 4WD control module self-test
DTCs. If a self-test DTC related to theconcern is retrieved, REFER to the 4WD
Control Module Diagnostic Trouble Code
(DTC) Index. If no DTC related to theconcern is retrieved, GO to Pinpoint TestI.

CHECK FOR MECHANICAL 4X4 LOW DISENGAGEMENT AND
4X4 ENGAGEMENT• Apply the brake.
••

NOTICE: Make sure there is a clear area behind the vehicle
before backing up.
Shift the transmission to REVERSE and back the vehicle up 3.0
meters (10 feet) to relieve driveline wind-up.
Stop the vehicle.

(Continued)
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308-07A-9

Four Wheel Drive (4WD) Systems

308-07A-9

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST C: ELECTRONIC SHIFT FUNCTIONAL TEST (Continued)
C18

Test StepCHECK FOR MECHANICAL 4X4 LOW DISENGAGEMENT AND
4X4 ENGAGEMENT (Continued)
•

C19

C20

C21

C22

Drive the vehicle forward and execute tight turns on a hardsurface.
• NOTE: Driveline wind-up and tire scuff is present in both 4X4
and 4X4 LOW. However, vehicle speed is severely limited in
4X4 LOW.
Verify the presence of driveline wind-up and tire scuff. Also
verify the increased vehicle speed from when 4X4 LOW wasengaged.
• Did 4X4 engage and the vehicle speed increase?
CHECK THE 4X4 TO 2WD SHIFT• Stop the vehicle.
• Turn the MSS to 2WD and wait 20 seconds.
• Listen for relay clicks and gearmotor operation.
• Are the 4X4 and 4X4 LOW indicators OFF?

Result / Action to Take

ATTEMPT MECHANICAL ASSIST OF 4X4 DISENGAGEMENT• Drive the vehicle forward above 8 kmh (5 mph) for at least 20
seconds.
• Stop the vehicle.
• Observe the 4X4 and 4X4 LOW indicators.
• Are the 4X4 and 4X4 LOW indicators OFF?

VERIFY THE HUBLOCKS DISENGAGE• Raise and support the front tires off the ground until they can be
spun freely. Refer to Section 100-02.
• Rotate the left front tire one revolution forward and one
revolution backward, while observing the left front axle shaft anduniversal joint.
• Rotate the right front tire one revolution forward and one
revolution backward, while observing the right front axle shaft
and universal joint.
• Did either axle shaft rotate?
VERIFY THE TRANSFER CASE MECHANICALLY DISENGAGED• Apply the parking brake.
• Rotate the front driveshaft.
• Does the front driveshaft turn?

Yes

GO to C19.

No

4X4 LOW is mechanically bound or
locked. REPAIR the transfer case asnecessary. REFER to Section 308-07B.

Yes

GO to C21.

No

GO to C20.

Yes

GO to C21.

No

RETRIEVE 4WD control module self-test
DTCs. If a self-test DTC related to theconcern is retrieved, REFER to the 4WD
Control Module Diagnostic Trouble Code
(DTC) Index. If no DTC related to theconcern is retrieved, GO to Pinpoint Test
I.

Yes

GO to Pinpoint Test G.

No

GO to C22.

Yes

GO to C23.

No

The transfer case did not disengage from
4X4. REPAIR the transfer case asnecessary. REFER to Section 308-07B.
C23

C24

VERIFY THE HUBLOCKS WILL LOCK MANUALLY• Turn both hublocks to the LOCK position.
• Rotate the left front tire one revolution forward and one
revolution backward while observing the left front axle shaft anduniversal joint.
• Rotate the right front tire one revolution forward and one
revolution backward while observing the right front axle shaft
and universal joint.
• Do both axles rotate?
VERIFY THE HUBLOCKS WILL UNLOCK MANUALLY• Turn both hublocks to the AUTO position.
• Rotate the left front tire one revolution forward and one
revolution backward while observing the left front axle shaft anduniversal joint.
• Rotate the right front tire one revolution forward and one
revolution backward while observing the right front axle shaft
and universal joint.
• Does either axle rotate?

Yes

GO to C24.

No

INSTALL a new hublock. REFER to
Hublock in this section.

Yes

INSTALL a new hublock. REFER to
Hublock in this section.

No

The transfer case is operating correctly.
INSTRUCT the customer on correct
system operation.

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308-07A-10

Four Wheel Drive (4WD) Systems

308-07A-10

DIAGNOSIS AND TESTING (Continued)
Symptom Chart — Electronic Shift
Symptom Chart
Condition• No communication with the
4WD control module•

The vehicle does not shift
between 2WD and 4X4correctly•

The vehicle does not shift
between 4X4 and 4X4 LOW
modes correctly

•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•

•

The front axle is not engaging
correctly•

The 4X4 indicator is always
on—four wheel drive system
operates correctly•

The 4X4 LOW indicator isalways on

•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•

Possible Sources
4WD control module.
Central junction box (CJB).
CJB fuse(s).
Circuitry.
CJB fuse(s).
Mode select switch (MSS).
Transfer case shift relays.
Contact plate A, B, C, or D.
Gearmotor encoder assembly.
Circuitry.
4WD control module.
Transfer case mechanism.
CJB fuse(s).
MSS.
Park/neutral position switch.
Brake pedal position (BPP)
switch.
4WD control module.
Transfer case.
Digital transmission range(TR) sensor.
Anti-lock brake control(ABS) module.
Circuitry.
CJB fuse(s).
Pulse vacuum hublock (PVH)
solenoid.
4WD control module.
Circuitry.
Vacuum lines.
Hublocks.
Hub and bearing.
ABS module.
Circuitry.
Instrument cluster.
4WD control module.
PCM.
Circuitry.
Instrument cluster.
4WD control module.

•

ActionGO to Pinpoint Test D.

•

GO to Pinpoint Test E.

•

GO to Pinpoint Test F.

•

GO to Pinpoint Test G.

•

GO to Pinpoint Test H.

•

GO to Pinpoint Test I.

Pinpoint Tests — Electronic ShiftPINPOINT TEST D: NO COMMUNICATION WITH THE 4WD CONTROL MODULE
D1Test StepCHECK VOLTAGE TO THE 4WD CONTROL MODULE• Ignition OFF.
• Disconnect: 4WD Control Module C281a.
• Disconnect: 4WD Control Module C281c.
• Ignition ON.

Result / Action to Take(Continued)

2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-11

Four Wheel Drive (4WD) Systems

308-07A-11

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST D: NO COMMUNICATION WITH THE 4WD CONTROL MODULE (Continued)
D1

Test StepCHECK VOLTAGE TO THE 4WD CONTROL MODULE(Continued)••

Result / Action to TakeOn all early production models, measure the voltage between
4WD control module C281a, pin18, circuit 640 (RD/YE) andground; 4WD control module C281c, pin14, circuit 1002 (BK/PK)
and ground; 4WD control module C281c, pin 5, circuit 22(LB/BK) and ground and between CJB C281c pin 11, circuit 22(LB/BK) and ground.
On all late production models, measure the voltage between
4WD control module C281a, pin 18, circuit 640 (RD/YE) andground; 4WD control module C281c, pin14, circuit 1002 (BK/PK)
and ground; 4WD control module C281c, pin 5, circuit 1306
(PK/WT) and ground and between 4WD control module C281c
pin 11, circuit 1306 (PK/WT) and ground.

Yes

GO to D2.

No

D2• Are the voltages greater than 10 volts?
CHECK CIRCUIT 676 (BK) FOR OPEN
• Measure the resistance between 4WD control module C281a pin
26, circuit 57 (BK), harness side and ground.

REPAIR the power supply circuits asnecessary. TEST the system for normal
operation.

Yes

REFER to Section 418-00.

No•

REPAIR the circuit. TEST the system fornormal operation.

Is the resistance less than 5 ohms?

PINPOINT TEST E: THE VEHICLE DOES NOT SHIFT BETWEEN 2WD AND 4X4 CORRECTLY
E1Test StepCHECK THE IGNITION STATES — MONITOR THE 4WD
CONTROL MODULE IGNITION PIDs
• NOTE: If the vehicle is equipped with a manual transmission,
depress the clutch pedal while turning the ignition switch to the
START position.
Monitor the 4WD control module ignition switch PIDs whileturning the ignition switch through all positions.

Result / Action to Take(Continued)

2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-12

Four Wheel Drive (4WD) Systems

308-07A-12

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST E: THE VEHICLE DOES NOT SHIFT BETWEEN 2WD AND 4X4 CORRECTLY (Continued)
E1

Test StepCHECK THE IGNITION STATES — MONITOR THE 4WD
CONTROL MODULE IGNITION PIDs (Continued)

Result / Action to Take

Ignition Switch
Position

PID

Expected ValueOFF

IGN O/LOFF

ACCESSORY

IGN ACC

ACCY

RUN

IGN R

RUN

START

IGN S

START

E2

Yes

GO to E2.

• Do the PID values agree with the ignition switch positions?
RETRIEVE THE DIAGNOSTIC TROUBLE CODES (DTCs)• Enter the following diagnostic mode on the scan tool: 4WD
Control Module Self-Test.
• Are any DTCs retrieved?

No

REFER to Section 211-05.

Yes

If DTC P1812, GO to E4.
If DTC P1815, GO to E4.
If DTC P1820, GO to E12.
If DTC P1822, GO to E12.
If DTC P1828, GO to E19.
If DTC P1830, GO to E19.
If DTC P1865, GO to E35.
If DTC P1867, GO to E36.
If DTC P1820 and P1828 are retrieved
together, GO to E26.

No

GO to E3.
E3

VERIFY THE FUNCTION TEST HAS BEEN CARRIED OUT• Using the previous diagnostic procedure steps:• Was the electronic shift function test carried out?

Yes

GO to E4.

No

CARRY OUT the electronic shift function
test. REFER to Function Test — Electronic
Shift in this section.
E4

E5

CHECK THE MODE SELECT SWITCH (MSS) — MONITOR THE
4WD control module PID 4WD SW• Ignition ON.
• Monitor the 4WD control module PID 4WD SW while cycling
the MSS through 2WD, 4X4, and 4X4 LOW.
• Do the 4WD control module PID values agree with the MSS
switch positions?
CHECK THE MSS — ALL POSITIONS• Disconnect: MSS C284.
• Measure the resistance between MSS terminal 2 and terminal 3.
Refer to the following chart:

MSS Position

Resistance2WD

3,700-4,100 Ohms

4X4

1,050-1,150 Ohms

4X4 LOW

340-380 Ohms

Yes

GO to E10.

No

GO to E5.

(Continued)

2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-13

Four Wheel Drive (4WD) Systems

308-07A-13

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST E: THE VEHICLE DOES NOT SHIFT BETWEEN 2WD AND 4X4 CORRECTLY (Continued)
E5

Test StepCHECK THE MSS — ALL POSITIONS (Continued)

Result / Action to TakeYes

GO to E6.

No

E6

• Are the resistances within the specified values?
CHECK CIRCUIT 465 (WH/LB) FOR AN OPEN
• Disconnect: 4WD Control Module C281b.
• Measure the resistance between MSS C284 pin 3, circuit 465(WH/LB), harness side and 4WD control module C281b pin 4,
circuit 465 (WH/LB), harness side.

INSTALL a new MSS. REFER to Mode
Select Switch (MSS) in this section.
CLEAR the DTCs. REPEAT the self-test.

Yes

GO to E7.

No
E7

• Is the resistance less than 5 ohms?
CHECK CIRCUIT 780 (DB) FOR SHORT TO VOLTAGE• Ignition ON.
• Measure the voltage between 4WD control module C281b pin 3,
circuit 780 (DB), harness side and ground.

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

Yes

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

E8• Is any voltage present?
CHECK CIRCUIT 780 (DB) FOR AN OPEN
• Ignition OFF.

No

GO to E8.

(Continued)
2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-14

Four Wheel Drive (4WD) Systems

308-07A-14

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST E: THE VEHICLE DOES NOT SHIFT BETWEEN 2WD AND 4X4 CORRECTLY (Continued)
E8

Test StepCHECK CIRCUIT 780 (DB) FOR AN OPEN (Continued)•

Result / Action to Take

Measure the resistance between MSS C284 pin 2, circuit 780(DB), harness side and 4WD control module C281b pin 3, circuit
780 (DB), harness side.

Yes

GO to E9.

No
E9• Is the resistance less than 5 ohms?
CHECK CIRCUIT 780 (DB) FOR A SHORT TO GROUND• Measure the resistance between 4WD control module C281b pin
3, circuit 780 (DB), harness side and ground.

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

Yes

GO to E57.

No
E10

• Is the resistance greater than 10,000 ohms?
CHECK THE VOLTAGE TO THE GEARMOTOR ENCODERASSEMBLY• Disconnect: Gearmotor Encoder Assembly C350b.

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

(Continued)

2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-15

Four Wheel Drive (4WD) Systems

308-07A-15

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST E: THE VEHICLE DOES NOT SHIFT BETWEEN 2WD AND 4X4 CORRECTLY (Continued)
E10

Test StepCHECK THE VOLTAGE TO THE GEARMOTOR ENCODERASSEMBLY (Continued)•

Result / Action to Take

NOTE: Voltage is only applied to the transfer case assembly forsix seconds while the 4WD control module active command
CW/CCW is ON.
Measure the voltage between gearmotor encoder assembly
C350b, pin 2, circuit 778 (OG), harness side and ground while
triggering the 4WD control module active command CW/CCW to
ON; and between gearmotor encoder assembly C350b, pin 1,
circuit 777 (YE), harness side and ground while triggering the
4WD control module active command CW/CCW to ON.

Yes

GO to E11.

No

E11

• Are the voltages greater than 10 volts?
CHECK THE VOLTAGE TO THE GEARMOTOR ENCODERASSEMBLY• Measure the voltage between gearmotor encoder assembly
C350b, pin 1, circuit 777 (YE), harness side and ground while
triggering the 4WD control module active command CW/CCW to
OFF; and between gearmotor encoder assembly C350b, pin 2,
circuit 778 (OG), harness side and ground while triggering the
4WD control module active command CW/CCW to OFF.

If there is no voltage on circuits 777 (YE)
and 778 (OG), GO to E26.
If there is no voltage on circuit 777 (YE)
only, GO to E12.
If there is no voltage on circuit 778 (OG)only, GO to E19.

Yes

GO to E56.

E12

• Are the voltages greater than 10 volts?
CHECK THE VOLTAGE TO THE GEARMOTOR ENCODERASSEMBLY LOW-TO-HIGH SHIFT RELAY — CIRCUIT 704(DG/LG)• Disconnect: Gearmotor Encoder Assembly Low-to-High Relay
C1129.
• Ignition ON.

No

GO to E31.

(Continued)

2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-16

Four Wheel Drive (4WD) Systems

308-07A-16

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST E: THE VEHICLE DOES NOT SHIFT BETWEEN 2WD AND 4X4 CORRECTLY (Continued)
E12

Test StepCHECK THE VOLTAGE TO THE GEARMOTOR ENCODERASSEMBLY LOW-TO-HIGH SHIFT RELAY — CIRCUIT 704(DG/LG) (Continued)•

Result / Action to Take

Measure the voltage between gearmotor encoder assembly
low-to-high relay C1129 pin 86, circuit 704 (DG/LG), harness
side and ground; and between gearmotor encoder assembly low
to high relay C1129 pin 87, circuit 704 (DG/LG), harness sideand ground.

Yes

GO to E13.

No
E13

E14

• Are the voltages greater than 10 volts?
CHECK THE GEARMOTOR ENCODER ASSEMBLY
LOW-TO-HIGH RELAY• Ignition OFF.
• Carry out the relay component test on the gearmotor encoder
assembly low-to-high relay. Refer to Refer to Wiring Diagrams
Cell 149 for component testing.
• Is the relay OK?

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

Yes

GO to E14.

No

INSTALL a new gearmotor encoder
assembly low-to-high relay. CLEAR the
DTCs. REPEAT the self-test.

CHECK CIRCUIT 782 (BN/WH) FOR A SHORT TO VOLTAGE• Disconnect: 4WD Control Module C281b.
• Ignition ON.
• Measure the voltage between gearmotor encoder assembly
low-to-high C1129 shift relay connector pin 85, circuit 782(BN/WH), harness side and ground.

Yes

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

E15• Is any voltage present?
CHECK CIRCUIT 782 (BN/WH) FOR OPEN
• Ignition OFF.

No

GO to E15.

(Continued)

2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-17

Four Wheel Drive (4WD) Systems

308-07A-17

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST E: THE VEHICLE DOES NOT SHIFT BETWEEN 2WD AND 4X4 CORRECTLY (Continued)
E15

Test StepCHECK CIRCUIT 782 (BN/WH) FOR OPEN (Continued)•

Result / Action to Take

Measure the resistance between gearmotor encoder assembly
low-to-high shift relay C1129 pin 85, circuit 782 (BN/WH),
harness side and 4WD control module C281b pin 10, circuit 782(BN/WH), harness side.

Yes

GO to E16.

No
E16• Is the resistance less than 5 ohms?
CHECK CIRCUIT 782 (BN/WH) FOR A SHORT TO GROUND• Measure the resistance between gearmotor encoder assembly
low-to-high shift relay C1129 pin 85, circuit 782 (BN/WH),
harness side and ground.

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

Yes

GO to E17.

No
E17

• Is the resistance greater than 10,000 ohms?
CHECK CIRCUIT 57 (BK) FOR AN OPEN
• Measure the resistance between gearmotor encoder assembly
low-to-high shift relay C1129 pin 87A, circuit 57 (BK), harness
side and ground.

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

Yes

GO to E18.

No•

Is the resistance less than 5 ohms?

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

(Continued)
2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-18

Four Wheel Drive (4WD) Systems

308-07A-18

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST E: THE VEHICLE DOES NOT SHIFT BETWEEN 2WD AND 4X4 CORRECTLY (Continued)
E18

Test StepCHECK CIRCUIT 777 (YE) FOR AN OPEN
• Disconnect: Gearmotor Encoder Assembly C350b.
• Measure the resistance between gearmotor encoder assembly
low-to-high relay C1129 pin 30, circuit 777 (YE), harness sideand gearmotor encoder assembly C350b, pin 1, circuit 777 (YE),harness side.

Result / Action to TakeYes

GO to E57.

No
E19

• Is the resistance less than 5 ohms?
CHECK THE VOLTAGE TO THE GEARMOTOR ENCODERASSEMBLY HIGH-TO-LOW RELAY• Remove the gearmotor encoder assembly high-to-low shift relay.
• Ignition ON.
• Measure the voltage between the gearmotor encoder assembly
high-to-low shift relay C1173 pin 86, circuit 704 (DG/LG),
harness side and ground; and between gearmotor encoder
assembly high-to-low shift relay C1173 pin 87, circuit 704(DG/LG), harness side and ground.

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

Yes

GO to E20.

No
E20

E21

• Are the voltages greater than 10 volts?
CHECK THE GEARMOTOR ENCODER ASSEMBLY
HIGH-TO-LOW RELAY• Carry out the relay component test on the gearmotor encoder
assembly high-to-low relay. Refer to Wiring Diagrams Cell 149
for component testing.
• Is the relay OK?

REPAIR the circuit. TEST the system fornormal operation.

Yes

GO to E21.

No

INSTALL a new gearmotor encoder
assembly high-to-low relay. CLEAR the
DTCs. REPEAT the self-test.

CHECK CIRCUIT 781 (OG/LB) FOR A SHORT TO VOLTAGE• Disconnect: 4WD Control Module C281b.
• Ignition ON.

(Continued)

2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-19

Four Wheel Drive (4WD) Systems

308-07A-19

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST E: THE VEHICLE DOES NOT SHIFT BETWEEN 2WD AND 4X4 CORRECTLY (Continued)
E21

Test StepCHECK CIRCUIT 781 (OG/LB) FOR A SHORT TO VOLTAGE(Continued)•

Result / Action to Take

Measure the voltage between gearmotor encoder assembly
high-to-low shift relay C1173 pin 85, circuit 781 (OG/LB),
harness side and ground.

Yes

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

E22• Is any voltage present?
CHECK CIRCUIT 781 (OG/LB) FOR AN OPEN
• Ignition OFF.
• Measure the resistance between gearmotor encoder assembly
high-to-low shift relay C1173 pin 85, circuit 781 (OG/LB),
harness side and 4WD control module C281b pin 11, circuit 781(OG/LB), harness side.

No

GO to E22.

Yes

GO to E23.

No•

Is the resistance less than 5 ohms?

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

(Continued)

2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-20

Four Wheel Drive (4WD) Systems

308-07A-20

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST E: THE VEHICLE DOES NOT SHIFT BETWEEN 2WD AND 4X4 CORRECTLY (Continued)
E23

Test StepCHECK CIRCUIT 781 (OG/LB) FOR A SHORT TO GROUND• Measure the resistance between gearmotor encoder assembly
high-to-low shift relay C1173 pin 85, circuit 781 (OG/LB),
harness side and ground.

Result / Action to TakeYes

GO to E24.

No
E24

• Is the resistance greater than 10,000 ohms?
CHECK HIGH TO LOW RELAY CIRCUIT 57 (BK) FOR AN OPEN
• Measure the resistance between gearmotor encoder assembly
high-to-low shift relay C1173 pin 87A, circuit 57 (BK), harness
side and ground.

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

Yes

GO to E25.

No
E25

• Is the resistance less than 5 ohms?
CHECK CIRCUIT 778 (OG) FOR AN OPEN
• Measure the resistance between gearmotor encoder assembly
high-to-low shift relay C1173 pin 30, circuit 778 (OG), harness
side and gearmotor encoder assembly C350b, pin 2, circuit 778(OG), harness side.

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

Yes

GO to E57.

No•

Is the resistance less than 5 ohms?

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

(Continued)
2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-21

Four Wheel Drive (4WD) Systems

308-07A-21

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST E: THE VEHICLE DOES NOT SHIFT BETWEEN 2WD AND 4X4 CORRECTLY (Continued)
E26

Test StepCHECK CENTRAL JUNCTION BOX (CJB) FUSE
• Remove the CJB fuse 111 (30A).
• Is the CJB fuse OK?

Result / Action to TakeYes

GO to E27.

No

GO to E28.
E27

CHECK VOLTAGE AT CJB FUSE
• Measure the voltage between CJB fuse 111 (30A) input terminaland ground.
• Is the voltage greater than 10 volts?

Yes

REPAIR circuit 704 (DG/LG). CLEAR the
DTCs. REPEAT the self-test.

No

REPAIR or install a new CJB as
necessary. CLEAR the DTCs. REPEAT
the self-test.
E28

CHECK CIRCUIT 704 (DG/LG) FOR A SHORT TO GROUND• Remove the gearmotor encoder assembly high-to-low shift relay.
• Remove the gearmotor encoder assembly low-to-high shift relay.
• Measure the resistance between gearmotor encoder assembly
high-to-low shift relay C1173 pin 86, circuit 704 (DG/LG),
harness side and ground; and between gearmotor encoder
assembly low-to-high shift relay C1129 pin 86, circuit 704(DG/LG), harness side and ground.

Yes

REPAIR the supply circuit. INSTALL a
new CJB fuse. CLEAR the DTCs.
REPEAT the self-test.

E29• Is the resistance less than 5 ohms?
CHECK SHIFT RELAY CIRCUIT 57 (BK) FOR AN OPEN
• Measure the resistance between the gearmotor encoder
assembly high-to-low shift relay C1173 pin 87A, circuit 57 (BK),
harness side and ground.

No

GO to E29.

Yes

GO to E30.

No
E30

• Is the resistance less than 5 ohms?
CHECK CIRCUITS 777 (YE) AND 778 (OG) FOR A SHORT TO
GROUND• Remove the gearmotor encoder assembly low-to-high shift relay.
• Disconnect: Gearmotor Encoder C350b.

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

(Continued)
2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-22

Four Wheel Drive (4WD) Systems

308-07A-22

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST E: THE VEHICLE DOES NOT SHIFT BETWEEN 2WD AND 4X4 CORRECTLY (Continued)
E30

Test StepCHECK CIRCUITS 777 (YE) AND 778 (OG) FOR A SHORT TO
GROUND (Continued)•

Result / Action to Take

Measure the resistance between gearmotor encoder assembly
C350b, pin 1, circuit 777 (YE), harness side and ground; andbetween gearmotor encoder assembly C350b, pin 2, circuit 778(OG), harness side and ground.

Yes

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

E31

E32

• Are the resistances less than 5 ohms?
REMOVE THE GEARMOTOR ENCODER ASSEMBLY FROM THE
TRANSFER CASE
• Ignition OFF.
• Remove the gearmotor encoder assembly. Refer to Gearmotor
Encoder Assembly in this section.
• Connect all connectors.
• Enter the following diagnostic mode on the scan tool: Clear all
DTCs.
• Start the vehicle and allow to idle.
• Ignition OFF.
• Ignition ON.
• Apply the parking brake.
• Press the brake pedal.
• Shift the transmission to NEUTRAL, for manual transmission
press and hold the clutch pedal.
• Monitor 4WD control module PID VSS2, BOO and NTRL_SW.
For manual transmission include, CLTCHSW.
• Do the PID values reflect the vehicle condition?
CHECK THE CONTACT PLATE ENCODER SWITCH• Monitor mode select switch (MSS) PIDs 2WD, 4X4 and 4X4
LOW.
• Monitor contact plate PIDs PLATE A, PLATE B, PLATE C
and PLATE D.
• Cycle the MSS to 2WD, 4X4 and 4X4 LOW two times.
• Compare the contact plate PID values for each shift position
selected by the MSS.

Plate PIDMSS PID2WD

MSS PID
4WD

MSS PID
4LOW

PLATE

A

OPEN

CLOSED

CLOSED

PLATE

B

OPEN

OPEN

CLOSED

PLATEC

CLOSED

CLOSED

OPEN

PLATE

D

OPEN

OPEN

OPEN

Do the contact plate PID values agree with the MSS switch
PIDs?
CHECK THE TRANSFER CASE
• Ignition OFF.
•

E33

No

GO to E57.

Yes

GO to E32.

No

GO to Pinpoint Test F.

Yes

GO to E33.

No

GO to E35.

(Continued)
2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-23

Four Wheel Drive (4WD) Systems

308-07A-23

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST E: THE VEHICLE DOES NOT SHIFT BETWEEN 2WD AND 4X4 CORRECTLY (Continued)
E33

Test StepCHECK THE TRANSFER CASE (Continued)

Result / Action to Take

•
•

E34

E35

Release the parking brake.
Using a wrench, manually shift the transfer case sector shaft tothe full clockwise (2WD) direction while turning the reardriveshaft.
• Engage the parking brake.
• Rotate the front driveshaft.
• Does the front driveshaft turn?
CHECK THE SECTOR SHAFT TURNING EFFORTNOTE: The transfer case has four detented shift positions. The fullclockwise position is 2WD, the next position is 4X4, then NEUTRAL
and the full counterclockwise position is 4X4 LOW. Normal
operation should not take more than 45 Nm (33 lb-ft) to manuallyshift the transfer case.
• Release the parking brake.
• Using a torque wrench, manually shift the transfer case sector
shaft in a counterclockwise direction to the 4X4 detent position
while rotating the rear driveshaft.
• Did the torque required to shift exceed 45 Nm (33 lb-ft)?
CHECK THE TRANSFER CASE SHIFT TO 4X4 AND 4X4 LOW• Apply the parking brake.
• Rotate the front driveshaft.
• Does the front driveshaft rotate?

Yes

GO to E34.

No

REPAIR the transfer case. REFER to
Section 308-07B. TEST the system fornormal operation.

Yes

REPAIR the transfer case as necessary.
REFER to Section 308-07B. TEST thesystem for normal operation.

No

GO to E35.

Yes

REPAIR the transfer case as necessary.
REFER to Section 308-07B.

No

INSTALL a new gearmotor encoder
assembly. REFER to Gearmotor Encoder
Assembly in this section. CLEAR the
DTCs. REPEAT the self-test.
E36

CHECK CONTACT PLATE GROUND CIRCUIT• Disconnect: Gearmotor Encoder Assembly C350a.
• On early production models, measure the resistance between
gearmotor encoder assembly C350a pin 4, circuit 870 (VT/YE),
harness side and ground.
• On late production models, measure the resistance between
gearmotor encoder assembly C350a, pin 4, circuit 3659 (BK/PK),
harness side and ground.

Yes

GO to E38.

E37

• Is the resistance less than 5 ohms?
CHECK CONTACT PLATE CIRCUIT FOR AN OPEN
• Disconnect: 4WD Control Module C281a.
• On early production models, measure the resistance between
gearmotor encoder assembly C350a pin 4, circuit 870 (PK/YE),
harness side and 4WD control module C281a pin 9, circuit 870(PK/YE), harness side and ground.

No

GO to E37.

(Continued)

2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-24

Four Wheel Drive (4WD) Systems

308-07A-24

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST E: THE VEHICLE DOES NOT SHIFT BETWEEN 2WD AND 4X4 CORRECTLY (Continued)
E37

Test StepCHECK CONTACT PLATE CIRCUIT FOR AN OPEN (Continued)•

Result / Action to Take

On late production models, measure the resistance between
gearmotor encoder assembly C350a, pin 4, circuit 3659 (BK/PK),
harness side and 4WD control module C281a pin 9, circuit 3659
(BK/PK), harness side and ground.

Yes

GO to E58.

No
E38

• Is the resistance less than 5 ohms?
CHECK CIRCUIT 976 (OG) FOR CONTACT PLATE VOLTAGE
SUPPLY• Ignition ON.
• Measure the voltage between gearmotor encoder assembly
C350a pin 2, circuit 976 (OG), harness side and ground. For
Excursion, the voltage should cycle between 0 volts and 1 to 3
volts. All others should be greater than 9 volts.

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

Yes

GO to E41.
Is the voltage reading as specified for the vehicle being
tested?
CHECK CIRCUIT 976 (OG) FOR A SHORT TO GROUND• Disconnect: 4WD Control Module C281a.
•
E39

No

GO to E39.

(Continued)

2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-25

Four Wheel Drive (4WD) Systems

308-07A-25

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST E: THE VEHICLE DOES NOT SHIFT BETWEEN 2WD AND 4X4 CORRECTLY (Continued)
E39

Test StepCHECK CIRCUIT 976 (OG) FOR A SHORT TO GROUND(Continued)•

Result / Action to Take

Measure the resistance between gearmotor encoder assembly
C350a pin 2, circuit 976 (OG), harness side and ground.

Yes

GO to E40.

No
E40

• Is the resistance greater than 10,000 ohms?
CHECK CIRCUIT 976 (OG) FOR AN OPEN
• Measure the resistance between gearmotor encoder assembly
C350a pin 2, circuit 976 (OG), harness side and 4WD control
module C281b pin 5, circuit 976 (OG), harness side.

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

Yes

GO to E58.

No
E41

• Is the resistance less than 5 ohms?
CHECK CONTACT PLATE SWITCH A— CIRCUIT 771 (VT/YE)• Connect: 4WD Control Module C281b.
• Monitor the 4WD control module PID: PLATE A.
• Connect a jumper wire between gearmotor encoder assembly
C350a pin 5, circuit 771 (VT/YE), harness side and ground.

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

Yes

GO to E45.
•

Does the PID: PLATE A toggle between CLOSED and
OPEN when ground is removed and applied?

No

GO to E42.

(Continued)
2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-26

Four Wheel Drive (4WD) Systems

308-07A-26

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST E: THE VEHICLE DOES NOT SHIFT BETWEEN 2WD AND 4X4 CORRECTLY (Continued)
E42

Test StepCHECK CIRCUIT 771 (VT/YE) FOR A SHORT TO VOLTAGE• Measure the voltage between gearmotor encoder assembly
C350a pin 5, circuit 771 (VT/YE), harness side and ground.

Result / Action to TakeYes

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

E43• Is voltage present?
CHECK CIRCUIT 771 (VT/YE) FOR A SHORT TO GROUND• Measure the resistance between gearmotor encoder assembly
C350a pin 5, circuit 771 (VT/YE), harness side and ground.

No

GO to E43.

Yes

GO to E44.

No
E44

• Is the resistance greater than 10,000 ohms?
CHECK CIRCUIT 771 (VT/YE) FOR AN OPEN
• Measure the resistance between gearmotor encoder assembly
C350a pin 5, circuit 771 (VT/YE), harness side and 4WD control
module C281b pin 15, circuit 771 (VT/YE), harness side.

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

Yes

GO to E58.

No
E45

• Is the resistance less than 5 ohms?
CHECK THE CONTACT PLATE SWITCH B — CIRCUIT 764(BN/WH)• Monitor the 4WD control module PID: PLATE B.

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

(Continued)
2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-27

Four Wheel Drive (4WD) Systems

308-07A-27

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST E: THE VEHICLE DOES NOT SHIFT BETWEEN 2WD AND 4X4 CORRECTLY (Continued)
E45

Test StepCHECK THE CONTACT PLATE SWITCH B — CIRCUIT 764(BN/WH) (Continued)•

Result / Action to Take

Connect a jumper wire between gearmotor encoder assembly,
C350a pin 3, circuit 764 (BN/WH), harness side and ground.

Yes

GO to E49.
Does the PID: PLATE B toggle between CLOSED and
OPEN when ground is removed and applied?
CHECK CIRCUIT 764 (BN/WH) FOR SHORT TO VOLTAGE• Measure the voltage between gearmotor encoder assembly
C350a pin 3, circuit 764 (BN/WH), harness side and ground.
•
E46

No

GO to E46.

Yes

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

E47• Is voltage present?
CHECK CIRCUIT 764 (BN/WH) FOR A SHORT TO GROUND• Measure the resistance between gearmotor encoder assembly
C350a pin 3, circuit 764 (BN/WH), harness side and ground.

No

GO to E47.

Yes

GO to E48.

No
E48

• Is the resistance greater than 10,000 ohms?
CHECK CIRCUIT 764 (BN/WH) FOR OPEN
• Disconnect: 4WD Control Module C281b.

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

(Continued)
2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-28

Four Wheel Drive (4WD) Systems

308-07A-28

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST E: THE VEHICLE DOES NOT SHIFT BETWEEN 2WD AND 4X4 CORRECTLY (Continued)
E48

Test StepCHECK CIRCUIT 764 (BN/WH) FOR OPEN (Continued)•

Result / Action to Take

Measure the resistance between gearmotor encoder assembly
C350a pin 3, circuit 764 (BN/WH), harness side and 4WD
control module C281b pin 17, circuit 764 (BN/WH), harness side.

Yes

GO to E58.

No
E49

• Is the resistance less than 5 ohms?
CHECK CONTACT PLATE SWITCH C — CIRCUIT 770 (WH)• Monitor the 4WD control module PID: PLATE C.
• Connect a jumper wire between gearmotor encoder assembly
C350a pin 6, circuit 770 (WH), harness side and ground.

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

Yes

GO to E53.
Does the PID: PLATE C toggle between CLOSED and
OPEN when ground is removed and applied?
CHECK CIRCUIT 770 (WH) FOR SHORT TO POWER• Measure the voltage between gearmotor encoder assembly
C350a pin 6, circuit 770 (WH), harness side and ground.
•
E50

No

GO to E50.

Yes

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.
•

Is any voltage present?

No

GO to E51.

(Continued)

2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-29

Four Wheel Drive (4WD) Systems

308-07A-29

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST E: THE VEHICLE DOES NOT SHIFT BETWEEN 2WD AND 4X4 CORRECTLY (Continued)
E51

Test StepCHECK CIRCUIT 770 (WH) FOR A SHORT TO GROUND• Measure the resistance between gearmotor encoder assembly
C350a pin 6, circuit 770 (WH), harness side and ground.

Result / Action to TakeYes

GO to E52.

No
E52

• Is the resistance greater than 10,000 ohms?
CHECK CIRCUIT 770 (WH) FOR AN OPEN
• Disconnect: 4WD Control Module C281b.
• Measure the resistance between gearmotor encoder assembly
C350a pin 6, circuit 770 (WH), harness side and 4WD control
module C281b pin 18, circuit 770 (WH), harness side.

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

Yes

GO to E58.

No
E53

• Is the resistance less than 5 ohms?
CHECK CONTACT PLATE SWITCH D — CIRCUIT 763 (OG/WH)• Monitor the 4WD control module PID: PLATE D.
• Connect jumper wire between gearmotor encoder assembly
C350a pin 1, circuit 763 (OG/WH), harness side and ground.

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

Yes

INSTALL a new gearmotor encoder
assembly. REFER to Gearmotor Encoder
Assembly in this section. CLEAR the
DTCs. REPEAT the self-test.
•

Does the PID: PLATE D toggle between CLOSED and
OPEN when ground is removed and applied?

No

GO to E54.

(Continued)
2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-30

Four Wheel Drive (4WD) Systems

308-07A-30

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST E: THE VEHICLE DOES NOT SHIFT BETWEEN 2WD AND 4X4 CORRECTLY (Continued)
E54

Test StepCHECK CIRCUIT 763 (OG/WH) FOR A SHORT TO VOLTAGE• Measure the voltage between gearmotor encoder assembly
C350a pin 1, circuit 763 (OG/WH), harness side and ground.

Result / Action to TakeYes

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

E55• Is any voltage present?
CHECK CIRCUIT 763 (OG/WH) FOR A SHORT TO GROUND• Measure the resistance between gearmotor encoder assembly
C350a pin 1, circuit 763 (OG/WH), harness side and ground.

No

GO to E55.

Yes

GO to E56.

No
E56

• Is the resistance greater than 10,000 ohms?
CHECK CIRCUIT 763 (OG/WH) FOR OPEN
• Disconnect: 4WD Control Module C281b.
• Measure the resistance between gearmotor encoder assembly
C350a pin 1, circuit 763 (OG/WH), harness side and 4WD
control module C281b pin 16, circuit 763 (OG/WH), harness
side.

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

Yes

GO to E58.

No•

Is the resistance less than 5 ohms?

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

(Continued)

2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-31

Four Wheel Drive (4WD) Systems

308-07A-31

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST E: THE VEHICLE DOES NOT SHIFT BETWEEN 2WD AND 4X4 CORRECTLY (Continued)
E57

Test StepCHECK CIRCUIT 777 (YE) AND 778 (OG) FOR A SHORT TO
VOLTAGE• Remove the gearmotor encoder high-to-low shift relay.
• Remove the gearmotor encoder low-to-high shift relay.
• Measure the voltage between gearmotor encoder assembly
C350b, pin 1, circuit 777 (YE), harness side and ground; andbetween gearmotor encoder assembly C350b, pin 2, circuit 778(OG), harness side and ground.

Result / Action to TakeYes

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

No

E58

• Is any voltage present?
CHECK FOR CORRECT MODULE OPERATION• Check for:• corrosion• pushed-out pins
• Connect any disconnected connectors making sure they areseated correctly.
• Make sure all other system connectors are fully seated.
• Operate the system and verify the concern is still present.
• Is the concern still present?

CARRY OUT the ISO Relay Component
Test on both shift relays. Refer to Wiring
Diagrams Cell 149 for component testing.
CLEAR the DTCs. REPEAT the self-test.

Yes

INSTALL a new 4WD control module.
REFER to Four Wheel Drive (4WD)
Control Module in this section. CLEAR the
DTCs. REPEAT the self-test.

No

The system is operating correctly at thistime. Concern may have been caused bya loose or corroded connector. CLEAR the
DTCs. REPEAT the self-test.

PINPOINT TEST F: THE VEHICLE DOES NOT SHIFT BETWEEN 4X4 AND 4X4 LOW MODES CORRECTLY
F1Test StepCHECK THE IGNITION STATES — MONITOR THE 4WD
CONTROL MODULE IGNITION PIDs
• NOTE: If the vehicle is equipped with a manual transmission,
depress the clutch pedal while turning the ignition switch to the
START position.
Monitor the 4WD control module ignition switch PIDs whileturning the ignition switch through all positions.

Ignition Switch
Position

PID

Expected ValueOFF

IGN O/LOFF

ACCESSORY

IGN ACC

ACCY

RUN

IGN R

RUN

START

IGN S

START

•

Result / Action to TakeYes

GO to F2.

Do the PID values agree with the ignition switch positions?

No

REFER to Section 211-05.

(Continued)

2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-32

Four Wheel Drive (4WD) Systems

308-07A-32

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST F: THE VEHICLE DOES NOT SHIFT BETWEEN 4X4 AND 4X4 LOW MODES CORRECTLY(Continued)
F2

Test StepRETRIEVE THE DIAGNOSTIC TROUBLE CODES (DTCs)• Using the results from the 4WD control module self-test:• Are any DTCs recorded?

Result / Action to Take

Yes

If DTC P0500, GO to F17.
If DTC B1483, GO to F10.
If DTC B1485, GO to F10.
If DTC P1812, GO to F4.
If DTC P1815, GO to F4.
If DTC P1819, GO to F13.

No

GO to F3.
F3VERIFY THE FUNCTION TEST HAS BEEN CARRIED OUT• Check the previous diagnostic procedure.
• Was the electronic shift function test carried out?

Yes

GO to F4.

NoCARRY OUT the electronic shift function
test. REFER to Function Test — Electronic
Shift in this section.
F4F5CHECK THE MODE SELECT SWITCH (MSS) — MONITOR THE
4WD CONTROL MODULE PID 4WD SW• Ignition ON.
• Monitor the 4WD control module PID 4WD SW while cycling
the MSS through 2WD, 4X4, and 4X4 LOW.
• Do the 4WD control module PID values agree with the MSS
switch positions?
CHECK THE MSS — ALL POSITIONS• Disconnect: MSS C284.
• Measure the resistance between MSS terminal 2 and terminal 3.
Refer to the following chart:

MSS Position

Resistance2WD

3,700-4,100 ohms

4X4

1,050-1,150 ohms

4X4 LOW

340-380 ohms

Yes

GO to F10.

No

GO to F5.

Yes

GO to F6.

No

F6• Are the resistances within the specified values?
CHECK CIRCUIT 465 (WH/LB) FOR AN OPEN
• Disconnect: 4WD Control Module C281b.

INSTALL a new MSS. REFER to Mode
Select Switch (MSS) in this section.
CLEAR the DTCs. REPEAT the self-test.

(Continued)

2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-33

Four Wheel Drive (4WD) Systems

308-07A-33

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST F: THE VEHICLE DOES NOT SHIFT BETWEEN 4X4 AND 4X4 LOW MODES CORRECTLY(Continued)
F6

Test StepCHECK CIRCUIT 465 (WH/LB) FOR AN OPEN (Continued)•

Result / Action to Take

Measure the resistance between MSS C284 pin 3, circuit 465(WH/LB), harness side and 4WD control module C281b pin 4,
circuit 465 (WH/LB), harness side.

Yes

GO to F7.

No
F7• Is the resistance less than 5 ohms?
CHECK CIRCUIT 780 (DB) FOR SHORT TO VOLTAGE• Ignition ON.
• Measure the voltage between 4WD control module C281b pin 3,
circuit 780 (DB), harness side and ground.

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

Yes

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

F8• Is any voltage present?
CHECK CIRCUIT 780 (DB) FOR AN OPEN
• Ignition OFF.
• Measure the resistance between MSS C284 pin 2, circuit 780(DB), harness side and 4WD control module C281b pin 3, circuit
780 (DB), harness side.

No

GO to F8.

Yes

GO to F9.

No•

Is the resistance less than 5 ohms?

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

(Continued)
2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-34

Four Wheel Drive (4WD) Systems

308-07A-34

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST F: THE VEHICLE DOES NOT SHIFT BETWEEN 4X4 AND 4X4 LOW MODES CORRECTLY(Continued)
F9

Test StepCHECK CIRCUIT 780 (DB) FOR A SHORT TO GROUND• Measure the resistance between 4WD control module C281b pin
3, circuit 780 (DB), harness side and ground.

Result / Action to TakeYes

GO to F20.

No
F10

F11

• Is the resistance greater than 10,000 ohms?
CHECK BRAKE PEDAL POSITION (BPP) SWITCH 4WD
CONTROL MODULE PID• Press and hold the brake pedal.
• Monitor the 4WD control module PID: BOO 4x4.
• Does the 4WD control module PID: BOO read ON when thebrake pedal is depressed and OFF when the brake pedal isreleased?
CHECK THE BRAKE LAMPS• Press and hold the brake pedal.
• Did the brake lamps illuminate?

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

Yes

GO to F13.

No

GO to F11.

Yes

GO to F12.

No

REFER to Section 417-01. CLEAR the
DTCs. REPEAT the self-test.
F12

CHECK CIRCUIT 810 (RD/LG) FOR AN OPEN
• Disconnect: 4WD Control Module C281b.
• Disconnect: BPP C278.
• Measure the resistance between BPP switch C278 pin 2, circuit
810 (RD/LG), harness side and 4WD control module C281b pin
12, circuit 810 (RD/LG), harness side.

Yes

GO to F13.

No
F13

• Is the resistance less than 5 ohms?
CHECK THE DIGITAL TR SENSOR PID NTRL SW• For manual transmission, monitor 4WD control module PID:
CLTCHSW. For automatic transmissions monitor 4WD control
module PID: NTRL SW.
• For automatic transmissions, place the transmission range
selector lever in NEUTRAL. For manual transmissions, press
and hold the clutch pedal.

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

(Continued)
2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-35

Four Wheel Drive (4WD) Systems

308-07A-35

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST F: THE VEHICLE DOES NOT SHIFT BETWEEN 4X4 AND 4X4 LOW MODES CORRECTLY(Continued)
F13

Test StepCHECK THE DIGITAL TR SENSOR PID NTRL SW (Continued)
•

F14

F15

For automatic transmissions, verify 4WD control module PID
reads NTRL. For manual transmissions, verify 4WD control
module PID: CLTCHSW reads ENGAGED.
• For automatic transmissions, shift the selector lever through all
positions while monitoring 4WD control module PID NTRL SW.
• For manual transmission: does the 4WD control module
PID: CLTCHSW read ENGAGED? For automatictransmission: does the 4WD control module PID: NTRL SW
read NTRL only for the NEUTRAL position?
CHECK THE DIGITAL TR SENSOR• Disconnect: Digital TR Sensor C167.
• Monitor 4WD control module PID: NTRL SW.
• Verify the 4WD control module PID: NTRL SW reads not
NTRL.
• Connect a jumper wire between digital TR sensor C167 pin 8,
circuit 463 (RD/WH), harness side and ground.
• Does the 4WD control module PID: NTRL SW indicate
NTRL?
CHECK CIRCUIT 463 (RD/WH) FOR AN OPEN
• Disconnect: 4WD Control Module C281b.
• Measure the resistance between digital TR sensor C167 pin 8,
circuit 463 (RD/WH), harness side and 4WD control module
C281b pin 1, circuit 463 (RD/WH), harness side.

Result / Action to TakeYes

GO to F17.

No

GO to F14.

Yes

REFER to Section 307-01A to diagnose
the digital TR sensor. CLEAR the DTCs.
REPEAT the self-test.

No

GO to F15.

Yes

GO to F16.

No
F16• Is the resistance less than 5 ohms?
CHECK CIRCUIT 463 (RD/WH) FOR A SHORT TO GROUND• Measure the resistance between digital TR sensor C167 pin 8,
circuit 463 (RD/WH), harness side and ground.

REPAIR the DTCs. CLEAR the DTCs.
REPEAT the self-test.

Yes

GO to F20.

No•

Is the resistance greater than 10,000 ohms?

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

(Continued)

2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-36

Four Wheel Drive (4WD) Systems

308-07A-36

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST F: THE VEHICLE DOES NOT SHIFT BETWEEN 4X4 AND 4X4 LOW MODES CORRECTLY(Continued)
F17

F18

Test StepCHECK THE VEHICLE SPEED SIGNAL• Monitor anti-lock brake module (ABS) PID: R WSSP.
• Monitor 4WD control module PID: VSS2 while driving the vehicle
0 to 88.5 km/h (55 mph) at a steady rate.
• Does the 4WD control module PID: VSS2 agree with ABS
PID: R WSSP?
CHECK THE SPEEDOMETER• Monitor the speedometer.
• Monitor 4WD control module PID: VSS2 while driving the vehicle
0 to 88.5 km/h (55 mph) at a steady rate.
• Does the 4WD control module PID: VSS2 agree withspeedometer?

Result / Action to TakeYes

GO to Pinpoint Test E.

No

GO to F18.

Yes

REFER to Section 413-01 to diagnose thespeedometer. CLEAR the DTCs. TEST thesystem for normal operation.

No

GO to F19.
F19

CHECK CIRCUIT 679 (GY/BK) FOR AN OPEN
• Disconnect: 4WD Control Module C281c.
• Disconnect: ABS C135.
• Measure the resistance between 4WD control module C281c,
pin 9, circuit 679 (GY/BK), harness side and ABS C135 pin 11,
circuit 679 (GY/BK), harness side.

Yes

GO to F20.

No
F20• Is the resistance less than 5 ohms?
CHECK FOR CORRECT MODULE OPERATION• Check for:• corrosion• pushed-out pins
• Connect any disconnected connectors making sure they seatcorrectly.
• Make sure all other system connectors are fully seated.
• Operate the system and verify the concern is still present.
• Is the concern still present?

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

Yes

INSTALL a new 4WD control module.
REFER to Four Wheel Drive (4WD)
Control Module in this section. CLEAR the
DTCs. REPEAT the self-test.

No

The system is operating correctly at thistime. Concern may have been caused bya loose or corroded connector. CLEAR the
DTCs. REPEAT the self-test.

PINPOINT TEST G: THE FRONT AXLE DOES NOT ENGAGE CORRECTLY
G1

Test StepRETRIEVE THE DIAGNOSTIC TROUBLE CODES (DTCs)• Refer to the recorded results of the 4WD control module
self-test.
• Were any DTCs retrieved?

Result / Action to Take

Yes

If DTC P1832, GO to G2.
If DTC P1834, GO to G5.
If DTC P1876, GO to G5.
If DTC P1877, GO to G7.

No

GO to G7.

(Continued)

2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-37

Four Wheel Drive (4WD) Systems

308-07A-37

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST G: THE FRONT AXLE DOES NOT ENGAGE CORRECTLY (Continued)
G2

Test StepCHECK FOR VOLTAGE TO THE PULSE VACUUM HUBLOCK(PVH) SOLENOID• Disconnect: PVH Solenoid C1247.
• Ignition ON.
• Measure the voltage between PVH solenoid C1247, pin 2, circuit
295 (LB/PK), harness side and ground.

Result / Action to TakeYes

GO to G3.

No
G3• Is the voltage greater than 10 volts?
CHECK CIRCUITS 605 (RD) AND 145 (GY/BK) FOR A SHORTTO VOLTAGE• Measure the voltage between PVH solenoid C1247, pin 3, circuit
605 (RD), harness side and ground; and between PVH solenoid
C1247, pin 1, circuit 145 (GY/BK), harness side and ground.

REPAIR circuit 295 (LB/BK). CLEAR the
DTCs. REPEAT the self-test.

Yes

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.
•

Is any voltage present?

No

GO to G4.

(Continued)

2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-38

Four Wheel Drive (4WD) Systems

308-07A-38

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST G: THE FRONT AXLE DOES NOT ENGAGE CORRECTLY (Continued)
G4

Test StepCHECK CIRCUITS 605 (RD) AND 145 (GY/BK) FOR A SHORTTO GROUND• Measure the resistance between PVH solenoid C1247, pin 3,
circuit 605 (RD), harness side and ground; and between PVH
solenoid C1247, pin 1, circuit 145 (GY/BK), harness side andground.

Result / Action to TakeYes

GO to G5.

No
G5• Are the resistances greater than 10,000 ohms?
CHECK CIRCUITS 605 (RD) AND 145 (GY/BK) FOR AN OPEN
• Disconnect: 4WD Control Module C281b.
• Measure the resistance between 4WD control module C281b pin
6, circuit 605 (RD), harness side and PVH solenoid C1247, pin
3, circuit 605 (RD), harness side.

•

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

Measure the resistance between 4WD control module C281b pin
7, circuit 145 (GY/BK), harness side and PVH solenoid C1247,
pin 1, circuit 145 (GY/BK), harness side.

Yes

GO to G6.

No•

Are the resistances less than 5 ohms?

REPAIR the circuit. CLEAR the DTCs.
REPEAT the self-test.

(Continued)

2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-39

Four Wheel Drive (4WD) Systems

308-07A-39

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST G: THE FRONT AXLE DOES NOT ENGAGE CORRECTLY (Continued)
G6

Test StepCHECK THE PVH SOLENOID COILS• Measure the resistance between the PVH solenoid terminal 1
and terminal 3; and measure the resistance between PVH
solenoid terminal 2 and terminal 3.

Result / Action to TakeYes

GO to G27.

No

G7

• Are the resistances between 45 and 55 ohms?
CHECK ENGAGE VACUUM SUPPLY TO THE RIGHT KNUCKLENOTE: The remaining steps require the use of a calibrated vacuum
gauge that is accurate to within a minimum of 0.1 in-Hg.
• Make sure hublocks are in the AUTO position.
• Lift and support the vehicle off the ground until the front tires
can be spun freely. Refer to Section 100-02.
• NOTE: The engine is required to be at idle during the following
steps to supply the vacuum required for the hublocks to engage
and disengage.
Start the engine and allow to idle.
• Turn the MSS to the 2WD position and wait 15 seconds. If
switching from 4X4 mode, wait an additional 45 seconds.
• Disconnect the vacuum line at the right front knuckle and installa vacuum gauge on the line.

INSTALL a new PVH solenoid. REFER to
Pulse Vacuum Hublock (PVH) Solenoid inthis section. CLEAR the DTCs. REPEAT
the self-test.

(Continued)

2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-40

Four Wheel Drive (4WD) Systems

308-07A-40

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST G: THE FRONT AXLE DOES NOT ENGAGE CORRECTLY (Continued)
G7

Test StepCHECK ENGAGE VACUUM SUPPLY TO THE RIGHT KNUCKLE(Continued)
•

•
•

G8

G9

G10

Result / Action to Take

Disconnect the vacuum line at the left front knuckle and plug theline.

Turn the MSS to 4X4.
NOTE: Normal operation applies engagement vacuum for 45
seconds and then drops to 0 in-Hg.
Observe the vacuum reading within 45 seconds.
• Is the vacuum reading greater than 10 in-Hg?
CHECK DISENGAGE VACUUM SUPPLY TO THE RIGHTKNUCKLE• Turn the MSS to 2WD.
• NOTE: Normal operation applies regulated disengagement
vacuum for 15 seconds and then drops to 0 in-Hg.
Observe the vacuum reading for 15 seconds.
• Is the vacuum reading between 147 and 180 mm-Hg (5.8 and
7.1 in-Hg)?
CHECK FOR MECHANICAL ENGAGEMENT AT THE RIGHTFRONT AXLE
• Remove the vacuum gauge and connect the vacuum line at theright front knuckle.
• Turn the MSS to 4X4.
• Wait one minute.
• Rotate the right front tire one revolution forward and one
revolution backward while observing the right front axle shaft
and universal joint.
• Did the right front axle shaft and universal joint turn?
CHECK FOR MECHANICAL DISENGAGEMENT AT THE RIGHTFRONT AXLE
• Turn the MSS to 2WD.
• Wait one minute.
• Rotate the right front tire one revolution forward and one
revolution backward, while observing the right front axle shaft
and universal joint.
• Did the right front axle shaft and universal joint turn?

Yes

GO to G8.

No

GO to G17.

Yes

GO to G9.

No

GO to G18.

Yes

GO to G10.

No

GO to G20.

Yes

GO to G20.

No

GO to G11.

(Continued)

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308-07A-41

Four Wheel Drive (4WD) Systems

308-07A-41

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST G: THE FRONT AXLE DOES NOT ENGAGE CORRECTLY (Continued)
G11

Test StepCHECK ENGAGE VACUUM SUPPLY TO THE LEFT KNUCKLE• Remove the plug from the vacuum line at the left front knuckle
and install the vacuum gauge on the line.

•

Result / Action to Take

Disconnect the vacuum line at the right front knuckle and plug
the line.

Yes
•
•

G12

G13

G14

Turn the MSS to 4X4.
NOTE: Normal operation applies engagement vacuum for 45
seconds and then drops to 0 in-Hg.
Observe the vacuum reading for 45 seconds.
• Is the vacuum reading greater than 10 in-Hg?
CHECK DISENGAGE VACUUM SUPPLY TO THE LEFTKNUCKLE• Turn the MSS to 2WD.
• NOTE: Normal operation applies regulated disengagement
vacuum for 15 seconds and then drops to 0 in-Hg.
Observe the vacuum reading within 15 seconds.
• Is the vacuum reading between 5.8 and 7.3 in-Hg?
CHECK FOR MECHANICAL ENGAGEMENT AT THE LEFTFRONT AXLE
• Remove the vacuum gauge and connect the vacuum line at theleft front knuckle.
• Turn the MSS to 4X4.
• Wait one minute.
• Rotate the left front tire one revolution forward and one
revolution backward while observing the left front axle shaft anduniversal joint.
• Did the left front axle shaft and universal joint turn?
CHECK FOR MECHANICAL DISENGAGEMENT AT THE LEFTFRONT AXLE
• Turn the MSS to 2WD.

GO to G12.

NoCHECK the vacuum harness for damage
or an obstruction. REPAIR as necessary.
TEST the system for normal operation.

Yes

GO to G13.

NoCHECK the vacuum harness for damage
or an obstruction. REPAIR as necessary.
TEST the system for normal operation.

Yes

GO to G14.

No

GO to G20.

(Continued)

2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-42

Four Wheel Drive (4WD) Systems

308-07A-42

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST G: THE FRONT AXLE DOES NOT ENGAGE CORRECTLY (Continued)
G14

Test StepCHECK FOR MECHANICAL DISENGAGEMENT AT THE LEFTFRONT AXLE (Continued)
•
•

G15

G16

G17

Wait one minute.
Rotate the left front tire one revolution forward and one
revolution backward while observing the left front axle shaft anduniversal joint.
• Did the left front axle shaft and universal joint turn?
CHECK FOR DYNAMIC VACUUM LEAK AT LF KNUCKLE• Ignition OFF.
• Disconnect the vacuum line at the front knuckle.
• Connect a vacuum pump to the knuckle fitting and T in thevacuum gauge between the knuckle and the pump.
• Pump until 20 in-Hg is read.
• Rotate the left front tire for 30 seconds while observing vacuum
reading.
• Is the vacuum drop greater than 0.5 in-Hg in 30 seconds?
CHECK FOR DYNAMIC VACUUM LEAK AT RF WHEEL• Ignition OFF.
• Disconnect the vacuum line at the right front knuckle.
• Connect a vacuum pump to the knuckle fitting and T in thevacuum gauge between the knuckle and the pump.
• Pump until 20 in-Hg is read.
• Rotate the right front tire for 30 seconds while observing vacuum
reading.
• Is the vacuum drop greater than 0.5 in-Hg in 30 seconds?
CHECK THE MANIFOLD VACUUM SUPPLY• Make sure the engine is still at idle.
• Disconnect the vacuum harness from the PVH solenoid.

•

Result / Action to TakeYes

GO to G20.

No

GO to G15.

Yes

GO to G24.

No

GO to G16.

Yes

GO to G24.

No

The 4X4 system is operating correctly.
INSTRUCT the customer on correct
operation.

Connect a vacuum gauge to the reservoir output line at the PVH
solenoid connection.

Yes

GO to G18.

No•

Is the vacuum reading greater than 10 in-Hg?

REPAIR the vacuum supply as necessary.
REFER to the Powertrain
Control/Emissions Diagnosis (PC/ED)
manual. TEST the system for normal
operation.

(Continued)

2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-43

Four Wheel Drive (4WD) Systems

308-07A-43

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST G: THE FRONT AXLE DOES NOT ENGAGE CORRECTLY (Continued)
G18

Test StepCHECK THE PVH SOLENOID OUTPUT IN 2WD• Connect the vacuum harness to the PVH solenoid so only thereservoir output line is connected to the solenoid.

•

Connect a vacuum gauge to the PVH solenoid output port.

NOTE: Normal operation applies engagement vacuum for 45
seconds and then drops to 0 in-Hg.
Turn the MSS to 4X4 and wait 45 seconds.
• NOTE: Normal operation applies regulated disengagement
vacuum for 15 seconds and then drops to 0 in-Hg.
Turn the MSS to 2WD while observing the vacuum gauge.
• Is the vacuum reading between 5.8 and 7.3 in-Hg?
CHECK THE PVH SOLENOID OUTPUT IN 4X4• NOTE: Normal operation applies engagement vacuum for 45
seconds and then drops to 0 in-Hg.
Turn the MSS to 4X4 and observe the vacuum reading for 45
seconds.
• Is the vacuum reading greater than 10 in-Hg in 4X4?
•

G19

Result / Action to TakeYes

GO to G19.

No

INSTALL a new PVH solenoid. REFER to
Pulse Vacuum Hublock (PVH) Solenoid inthis section. TEST the system for normal
operation.

Yes

CHECK the vacuum harness for leaks,
restrictions, kinks or melted lines. REPAIR
the vacuum harness as necessary. TEST
the system for normal operation.

No

INSTALL a new PVH solenoid. REFER to
Pulse Vacuum Hublock (PVH) Solenoid inthis section. TEST the system for normal
operation.
G20

CHECK FOR A STATIC VACUUM LEAK
• Ignition OFF.
• Disconnect the vacuum line at the knuckle.

(Continued)

2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-44

Four Wheel Drive (4WD) Systems

308-07A-44

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST G: THE FRONT AXLE DOES NOT ENGAGE CORRECTLY (Continued)
G20

Test StepCHECK FOR A STATIC VACUUM LEAK (Continued)•

Result / Action to Take

Connect a vacuum pump to the knuckle fitting and T in thevacuum gauge between the knuckle and the pump.

Yes

G21

• Pump until 20 in-Hg is read.
• Observe the vacuum reading for 30 seconds.
• Is the vacuum drop less than 0.5 in-Hg in 30 seconds?
CHECK FOR A DYNAMIC VACUUM LEAK
• Make sure the vacuum is still at 20 in-Hg.
• Rotate the front tire for 30 seconds while observing the vacuum
reading.
• Is the vacuum drop less than 0.5 in-Hg in 30 seconds?

GO to G21.

No

GO to G22.

Yes

INSTALL a new hublock. TEST the system
for normal operation.

No

GO to G23.
G22

CHECK FOR A LOOSE KNUCKLE FITTING• Remove the vacuum pump and gauge line from the knuckle.
• Make sure the knuckle fitting is tightened to 20 Nm (15 lb-ft).
• Install the vacuum pump and gauge line on the knuckle andpump to 20 in-Hg.

Yes

If the right hublock was being tested, GO
to G9. If the left hublock was being tested,
GO to G13.

G23

• Observe the vacuum reading for 30 seconds.
• Is the vacuum drop less than 0.5 in-Hg in 30 seconds?
CHECK FOR A HUBLOCK O-RING LEAK
• Install a known good hublock. Refer to Hublock in this section.

No

GO to G23.

(Continued)

2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-45

Four Wheel Drive (4WD) Systems

308-07A-45

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST G: THE FRONT AXLE DOES NOT ENGAGE CORRECTLY (Continued)
G23

Test StepCHECK FOR A HUBLOCK O-RING LEAK (Continued)•

Result / Action to Take

Install the vacuum pump and gauge line on the knuckle andpump to 20 in-Hg.

Yes

Install a new hublock with a new O-ringseal kit. Refer to Hublock in this section

G24• Observe the vacuum reading for 30 seconds.
• Is the vacuum drop less than 0.5 in-Hg in 30 seconds?
CHECK THE HUBLOCK SEALS• Install the vacuum pump and gauge line on the knuckle fitting
and pump to 20 in-Hg.

No

GO to G24.

Yes

GO to G25.

G25

• Observe the vacuum reading for 30 seconds.
• Is the vacuum drop greater than 0.5 in-Hg in 30 seconds?
CHECK THE KNUCKLE SEAL
• Install a known good wheel knuckle with a known good hublock.
Refer to Section 204-01B.
• Install the vacuum pump and gauge line on the knuckle fitting
and pump to 20 in-Hg.

No

The 4X4 system is operating correctly.
TEST the system for normal operation.

Yes

GO to G26.

No••

Observe the vacuum reading for 30 seconds.
Is the vacuum drop less than 0.5 in-Hg in 30 seconds?

INSTALL a new knuckle seal. REFER to
Section 204-01B. TEST the system fornormal operation.

(Continued)
2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-46

Four Wheel Drive (4WD) Systems

308-07A-46

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST G: THE FRONT AXLE DOES NOT ENGAGE CORRECTLY (Continued)
G26

Test StepCHECK FOR A LEAKING HUB ASSEMBLY• Install the hub assembly with a new O-ring seal.
• Install the vacuum pump and gauge line on the knuckle fitting
and pump to 20 in-Hg.

Result / Action to TakeYes

REINSTALL the wheel knuckle assembly
and RESTORE the system to normal
condition. REFER to Section 204-01B.
VERIFY correct engagement of the 4X4
system.

No

G27• Observe the vacuum reading for 30 seconds.
• Is the vacuum drop less than 0.5 in-Hg in 30 seconds?
CHECK FOR CORRECT MODULE OPERATION• Check for:• corrosion• pushed-out pins
• Connect any disconnected connectors making sure they areseated correctly.
• Make sure all other system connectors are fully seated.
• Operate the system and verify the concern is still present.
• Is the concern still present?

INSTALL a new wheel knuckle assembly.
REFER to Section 204-01B. TEST thesystem for normal operation. If the leakpersists, INSTALL a new hublock. REFER
to Hublock in this section. TEST thesystem for normal operation.

Yes

INSTALL a new 4WD control module.
REFER to Four Wheel Drive (4WD)
Control Module in this section. CLEAR the
DTCs. REPEAT the self-test.

No

The system is operating correctly at thistime. Concern may have been caused bya loose or corroded connector. CLEAR the
DTCs. REPEAT the self-test.

PINPOINT TEST H: THE 4X4 INDICATOR IS ALWAYS ON—FOUR WHEEL DRIVE SYSTEM OPERATESCORRECTLY
H1

H2

Test StepMONITOR THE 4X4 INDICATOR• Verify the vehicle is in 2WD.
• Observe the 4X4 indicator.
• Disconnect the anti-lock brake (ABS) module C104.
• Ignition ON.
• Does the 4X4 indicator go off?
CHECK THE 4WD CONTROL MODULE• Disconnect: 4WD Control Module C281b.
• Does the 4X4 indicator go off?

Result / Action to TakeYes

REFER Section 206-09 for further
diagnosis.

No

GO to H2.

Yes

GO to H4.

No

GO to H3.
H3CHECK THE INSTRUMENT CLUSTER• Disconnect: Instrument Cluster C220b.
• Does the 4X4 indicator go off?

Yes

REPAIR circuit 210 (LB). TEST the system
for normal operation.

No

REPAIR the instrument cluster asnecessary. REFER to Section 413-01.
TEST the system for normal operation.

(Continued)

2003 Excursion, F-Super Duty 250-550, 1/2003

308-07A-47

Four Wheel Drive (4WD) Systems

308-07A-47

DIAGNOSIS AND TESTING (Continued)
PINPOINT TEST H: THE 4X4 INDICATOR IS ALWAYS ON—FOUR WHEEL DRIVE SYSTEM OPERATESCORRECTLY (Continued)
H4

Test StepCHECK FOR CORRECT MODULE OPERATION• Check for:• corrosion• pushed-out pins
• Connect any disconnected connectors making sure they areseated correctly.
• Make sure all other system connectors are fully seated.
• Operate the system and verify the concern is still present.
• Is the concern still present?

Result / Action to Take

Yes

INSTALL a new 4WD control module.
REFER to Four Wheel Drive (4WD)
Control Module in this section. CLEAR the
DTCs. REPEAT the self-test.

No

The system is operating correctly at thistime. Concern may have been caused bya loose or corroded connector. CLEAR the
DTCs. REPEAT the self-test.

PINPOINT TEST I: THE 4X4 LOW INDICATOR IS ALWAYS ON
I1

I2

Test StepMONITOR THE 4X4 LOW INDICATOR• Verify the vehicle is in 2-wheel drive mode.
• Observe the 4X4 LOW indicator.
• Disconnect: 4WD Control Module C281b.
• Ignition ON.
• Does the 4X4 LOW indicator go off?
CHECK THE INSTRUMENT CLUSTER• Disconnect: Instrument Cluster C220b.
• Does the 4X4 LOW indicator go off?

Result / Action to TakeYes

GO to I4.

No

GO to I2.

Yes

GO to I3.

No

REPAIR the instrument cluster asnecessary. REFER to Section 413-01.
TEST the system for normal operation.
I3

CHECK CIRCUIT 975 (BN/YE) FOR A SHORT TO GROUND• Measure the resistance between 4WD control module C281b pin
8, circuit 975 (BN/YE), harness side and ground.

Yes

GO to I4.

No
I4

• Is the resistance greater than 10,000 ohms?
CHECK FOR CORRECT MODULE OPERATION• Check for:• corrosion• pushed-out pins
• Connect any disconnected connectors making sure they seatcorrectly.
• Make sure all other system connectors are fully seated.
• Operate the system and verify the concern is still present.
• Is the concern still present?

REPAIR the circuit. TEST the system fornormal operation.

Yes

INSTALL a new 4WD control module.
REFER to Four Wheel Drive (4WD)
Control Module in this section. CLEAR the
DTCs. REPEAT the self-test.

No

The system is operating correctly at thistime. Concern may have been caused bya loose or corroded connector. CLEAR the
DTCs. REPEAT the self-test.

2003 Excursion, F-Super Duty 250-550, 1/2003